Relier Pairs Talking About FunctionsVersion en ligne Matching par Logos Sprachinstitut 1 The bridge is supported by steel pylons. 2 The vehicle is powered by the engine. 3 The shelf is bolted to the wall with screws. 4 The purpose of the backup file is to keep our data safe. 5 The airflow is regulated by the valve. 6 The purpose of the wheel is to steer the truck. 7 The function of the switch is to turn the machine on and off. The engine powers the vehicle. The wheel steers the truck. Steel pylons support the bridge. The switch turns the machine on and off. The backup file keeps our data safe. The valve regulates the airflow. Screws bolt the shelf to the wall.